The Relation between Solar Eruption Topologies and Observed Flare Features I: Flare Ribbons

TL;DR

This study investigates the magnetic topology of seven two-ribbon solar flares using 3D models, revealing strong correlations between quasi-separatrix layers and observed flare ribbons, and demonstrating the predictive power of the modeling technique.

Contribution

It presents the largest sample of QSLs derived from 3D coronal magnetic field models and validates the flux rope insertion method for predicting flare ribbon locations.

Findings

QSLs match flare ribbon segments well

Flux rope models accurately represent flaring regions

QSLs overlay ridges in electric current density maps

Abstract

In this paper we present a topological magnetic field investigation of seven two-ribbon flares in sigmoidal active regions observed with Hinode, STEREO, and SDO. We first derive the 3D coronal magnetic field structure of all regions using marginally unstable 3D coronal magnetic field models created with the flux rope insertion method. The unstable models have been shown to be a good model of the flaring magnetic field configurations. Regions are selected based on their pre-flare configurations along with the appearance and observational coverage of flare ribbons, and the model is constrained using pre-flare features observed in extreme ultraviolet and X-ray passbands. We perform a topology analysis of the models by computing the squashing factor, Q, in order to determine the locations of prominent quasi-separatrix layers (QSLs). QSLs from these maps are compared to flare ribbons at their full extents. We show that in all cases the straight segments of the two J-shaped ribbons are matched very well by the flux-rope-related QSLs, and the matches to the hooked segments are less consistent but still good for most cases. In addition, we show that these QSLs overlay ridges in the electric current density maps. This study is the largest sample of regions with QSLs derived from 3D coronal magnetic field models, and it shows that the magnetofrictional modeling technique that we employ gives a very good representation of flaring regions, with the power to predict flare ribbon locations in the event of a flare following the time of the model.